We are measuring baroreflex sensitivity in patients with essential hypertension and in normotensive controls using 8 different measurement techniques, in order to determine whether the techniques agree with eacth other, if baroreflex sensitivity is abnormal in essential hypertension, if clonidine exerts its antihypertensive action by affecting the baroreflex, if naloxone antagonizes clonidine's effects, and if normotensive children of hypertensive parents show any abnormal-mality of baroreflex-mediated circulatory control.